Method and apparatus for merging multiple geometrical pixel images and generating a single modulator pixel image

ABSTRACT

The present invention relates to customizing individual workpieces, such as chip, flat panels or other electronic devices produced on substrates, by direct writing a custom pattern. Customization can be per device, per substrate, per batch or at some other small volume that makes it impractical to use a custom mask or mask set. In particular, it relates to customizing a latent image formed in a patterning sensitive layer over a substrate, merging standard and custom pattern data to form a custom pattern used to produce the customized latent image. A wide variety of substrates can benefit from the technology disclosed.

RELATED APPLICATIONS

This application is related to and claims the benefit of U.S.Provisional Application No. 61/311,276 by the same title as this. Thepriority application is incorporated by reference. It is a continuationof U.S. Pat. No. 8,539,395 issuing on Sep. 17, 2013 by the same title.This application is further related to U.S. Pat. No. 7,328,425 entitled“Method and Device for Correcting SLM Stamp Image Imperfections”, U.S.Pat. No. 7,405,414 entitled “Method and Apparatus for Patterning aWorkpiece”, and U.S. Pat. No. 7,842,525 entitled “Method and Apparatusfor Personalization of Semiconductor”. It is further related to U.S.Patent Publication No. 2010/0142838 A1 entitled “Gradient AssistedResampling in Micro-Lithographic Printing”. It is also related to U.S.Patent Publication No. 2011/0216302 entitled “Illumination Methods andDevices for Partially Coherent Illumination”. The related patents,patent publication, and patent application are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

The present invention relates to customizing individual workpieces, suchas chips, flat panels or other electronic devices produced onsubstrates, by direct writing a custom pattern. Customization can be perdevice, per substrate, per batch or at some other small volume thatmakes it impractical to use a custom mask or mask set. In particular, itrelates to customizing a latent image formed in a radiation sensitivelayer over a substrate, merging standard and custom pattern data to forma custom pattern used to produce the customized latent image. A widevariety of substrates can benefit from the technology disclosed.

It is sometimes useful to permanently load an integrated circuit withcustom, personalized or unique information. This usefulness has led tothe development of a variety of one-time programmable or write-oncememories. One example is found in U.S. Pat. No. 6,813,182, entitled“Diode-and-Fuse Memory Elements for a Write-Once Memory Comprising anAnisotropic Semi Conductor Sheet.” The crosspoint memory elementdescribed can be converted from a fuse-intact state to fuse-blown stateonly once, thereby providing a write-once memory.

Another example is found in U.S. Patent Publication 2010/0001330A1,entitled “Semi Conductor Device, Data Element Thereof and Method ofFabricating the Same.” That application describes nonvolatile memoriesin categories of factory programmed ROMs, also called mask ROMs, andfield programmable memories.

In contrast to the fused memory approaches, the development team atMicronic Laser/Micronic Mydata has previously proposed combining thefeatures of a stepper with an SLM to optically merge standard data froma mask and custom data from the SLM. Two patents issued in this area oftechnology include U.S. Pat. Nos. 6,813,058 and 7,842,525, both entitled“Method and Apparatus for Personalization of Semiconductor.”

Accordingly, there is an opportunity to provide new technology forpermanently loading an integrated circuit with custom, personalized orunique information. New technologies may be better integrated intoproduction, more reliable, more flexible or more cost-effective.

SUMMARY OF THE INVENTION

The present invention relates to customizing individual workpieces, suchas integrated circuits, flat panels or other electronic devices producedon substrates, by direct writing a custom pattern. Customization can beper device, per substrate, per batch or at some other small volume thatmakes it impractical to use a custom mask or mask set. In particular, itrelates to customizing a latent image formed in a radiation sensitivelayer over a substrate, merging standard and custom pattern data to forma custom pattern used to produce the customized latent image. A widevariety of substrates can benefit from the technology disclosed.Particular aspects of the present invention are described in the claims,specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the general layout of an SLM pattern generator.

FIG. 2 depicts a scanning system with three arms and a pair ofworkpieces being written on opposite sides of the hub.

FIG. 3 depicts a generic data path that includes resampling to amodulator grid.

FIG. 4 is a high level block diagram of a data flow that merges standardand custom pattern data.

FIG. 5 illustrates a circular wafer and a rectangular substrate on whichmultiple dies are formed.

FIG. 6 depicts grids of different pixel size and tile size.

FIG. 7 depicts a variety of modulator and stage types used for producinglatent images.

DETAILED DESCRIPTION

The following detailed description is made with reference to thefigures. Preferred embodiments are described to illustrate the presentinvention, not to limit its scope, which is defined by the claims. Thoseof ordinary skill in the art will recognize a variety of equivalentvariations on the description that follows.

FIGS. 4-6 disclose resampling and merging of standard and custom dataand using the merged data to form a latent image in a radiationsensitive layer over a substrate by direct writing device for at leastone layer. Unlike the mixed stepper-SLM technology disclosed in U.S.Pat. Nos. 6,813,058 and 7,842,525, this technology uses direct writingtechnology for at least one layer and is compatible with using a steppertechnology or any preferred pattern generator for other layers.

FIG. 4 is a high level block diagram of a data flow that merges standardand custom pattern data. A merging and resampling component 433 receivesstandard pattern data 401 and custom pattern data 431 on two data paths.The data paths may be physically separate or interleaved, as on a singledata bus or memory access channel. By “data path,” we mean to refer tohow data is delivered to the resampling and merging component 433. Thedata may come from vector or raster data and may be stored on rotatingor non-rotating memory.

Design data, typically a vector data set, is converted into a commonvector format for manufacturing. Vector domain geometry processing isapplied in this format. The vector format is then rendered into ageometrical pixel map, producing what we refer to as “standard patterndata”. Pixel domain image processing is applied and the data isresampled into a modulator dependent format for printing.

For batch printing, where many identical or nearly identical panels areproduced, it is beneficial to reuse previously generated data, to avoidredoing the same work multiple times. However, in the progression ofimage format versions, the final modulator pixel map cannot be reused,because it carries compensations that are unique to a particular panelbeing imaged. Examples of such compensation include alignmentinformation and distortion compensation. Standard pattern data may begeneric across multiple panels and reused, or it may just be the basedata to which customization is applied. Reuse across panels means thatthe geometrical map is generated once, and then the same map is reusedfor multiple panels in a batch. That way, the computational effort islower and the hardware configuration can be smaller compared to when thegeometrical map has to be regenerated for each panel. The geometricalmap can be produced long before the actual printing is performed.Actually, multiple geometrical maps can be prepared in advance andarchived for later use. This scheme also permits inspection of the mapprior to printing.

Reusable standard pattern data inherently makes panels identical, whichtypically is desirable. However, there are use cases in whichindividuality is desired for some panel, or parts of some panel, such assubstrates for packaging purposes or memory elements for programmingpurposes. Examples of individuality include unit serial numbers,manufacturing batch or time and date, manufacturing substrate or othermanufacturing data. There are other cases in which edges of a dierequire different patterns than the main field of the die, for instancein large area masks. For these purposes, a second pixel map of custompattern data can be used. We disclose merging and resampling thestandard pattern data with the custom pattern data, for instance at thetime when the data is being used to form latent images.

The merging can be performed at various times, before or afterresampling. Accordingly, merging and resampling are represented by asingle component and may be claimed as a single action, because theorder of merging and resampling depends on the nature of the standardand custom pattern data. In some use cases, the merging can be donebefore resampling, allowing the processing to be performed off-line,where time is less critical. Then, on-line processing is more nearlytime-wise deterministic, allowing optimization of compute power. Theresampling operation transforms one input map into one output map, whichsimplifies the resampling operation. The combined pixel maps can beaccessed for inspection prior to printing.

When merging is performed during resampling, the custom pattern datapixel maps can be generated immediately before printing, immediatelybefore the modulator pixel map is generated. One example of recentcustom pattern data generated near the time of production the exactproduction time to be merged into the pattern.

When merging is performed after resampling, the additional pixel mapsmay also be merged into an existing modulator pixel map. This can bebeneficial when the data flow is partitioned in a way that requires amerge of multiple modulator pixel maps prior to printing.

During merging, the custom pattern data can be tested to determinewhether any customization is required in a particular area, frame ortile. If there is no customization, the merge can be optimized, whetherby bypassing the merge altogether or performing a merge that will notchange the pixel values in the standard pattern data. If there is nocustomization, there may be little or no custom pattern data to process.

The merge between the standard pattern data in the base geometricalpixel map and the custom pattern data in additional geometrical pixelmap(s) can be performed for matching or much different pixel grids.First, identical and aligned pixel grids can be merged. In the simplestform, the merge is performed on multiple pixel maps where the grids andtiles are matching, i.e., the pixel dimensions and the alignment of themaps are identical. In this case, the merged can be performed beforeresampling, pixel-to-pixel, with a simple merge operation. Alternativemerge operations are described below.

Second, identical but offset pixel grids can be merged. Here, the gridsof the multiple pixel maps have the same pixel dimensions, but areoffset so that a single pixel in one map does not correspond to a singlepixel in the other map. In this case, the offset can be removed bysnapping the offset of the additional maps to match the base map. Thenthe merge is performed before resampling, pixel-to-pixel, with a simplemerge operation. Or, multiple adjoining pixels in the additional map canbe resampled to decide the value of the resulting pixel to be merged.

Third, non-matching pixel grids can be merged. This is illustrated inFIG. 6, which depicts grids of different pixel size and tile size. Inthis illustration, the standard pattern data is in grid 601 and thecustom pattern data is in grid 611. Three pixels of custom data 613 fitover twelve pixels of standard data 605. A connecting pattern 613overlays pads 603 of an open gap. This is a simplification ofprogramming a custom pattern of ones and zeros as closed and openconnections. When the pixel grids are not matching, either by pitch oroffset, the merge can be performed by resampling the images to a commongrid and tile. Or, multiple grids could be resampled at the same timeand the resampling results merged.

When pixel grids match, the merge can be done pixel-by-pixel with asimple one-to-one merge operation. Depending on the data involved,different merge operations can be used, such as Replace, Add, Subtract,XOR, AND, OR. The operations Replace, Add and Subtract can be used forpixels are represented by floating point or integer values, but thelogical operations are difficult to apply to floating point values, dueto exponent scaling. If the pixels are represented by integer values,any of these merge operations can be applied.

Workpieces that can benefit from custom pattern data include silicon orsemiconductor wafers, circuit boards, flat-panel displays and substratesof flexible material used in roll-to-roll production. FIG. 5 illustratesa circular wafer 501 and a rectangular substrate on which multiple dies511, 515 are formed. The dies are separated to form chips or flat panelsubstrates.

The customization technology disclosed can be applied in a variety ofenvironments. The Micronic Laser development team has pioneered avariety of platforms for microlithographic printing. An establishedplatform for the Sigma machine is depicted in FIG. 1. A rotor printingplatform described in recently filed patent applications is depicted inFIG. 2. A drum printing platform is described in other patentapplications. FIG. 7 depicts a variety of modulator and stage types usedfor producing latent images. Some of these modulators and stages arecurrently in use and others have yet to be developed. In addition to thesystems depicted, scanner-based direct writing also have been described,particularly in collaborative work of Micronic Laser and ASML.

In the following paragraphs, we describe two environments that use a 2DSLM, which may benefit from use of the technology disclosed.

FIG. 1 depicts the general layout of an SLM pattern generator with a ofxy stage. The workpiece to be exposed sits on a stage 112. The positionof the stage is controlled by precise positioning device, such as pairedinterferometers 113.

The workpiece may be an integrated circuit or flat panel with a layer ofresist or other exposure sensitive material. In the first direction, thestage moves continuously. In the other direction, generallyperpendicular to the first direction, the stage either moves slowly ormoves in steps, so that stripes of stamps are exposed on the workpiece.In this embodiment, a flash command 108 is received at a pulsed Excimerlaser source 107, which generates a laser pulse. This laser pulse may bein the deep ultraviolet (DUV) or extreme ultraviolet (EUV) spectrumrange. The laser pulse is converted into an illuminating light 106 by abeam conditioner or homogenizer. Applying the technology disclosedherein, a continuous laser with the illuminator described could besubstituted for the pulsed laser, especially with the workpiece trackingoptics.

A beam splitter 105 directs at least a portion of the illuminating lightto an SLM 104. The pulses are brief, such as only 20 ns long, so anystage movement is frozen during the flash. The SLM 104 is responsive tothe datastream 101, which is processed by a pattern rasterizer 102. Inone configuration, the SLM has 2048×512 mirrors that are 16×16 μm eachand have a projected image of 80×80 nm. It includes a CMOS analog memorywith a micro-mechanical mirror formed half a micron above each storagenode.

The electrostatic forces between the storage nodes and the mirrorsactuate the mirrors. The device works in diffraction mode and needs todeflect the mirrors by only a quarter of the wavelength (62 nm at 248nm) to go from the fully on-state to the fully off-state. To create afine address grid the mirrors are driven to on, off and 63 intermediatevalues. The pattern is stitched together from millions of images of theSLM chip. Flashing and stitching proceed at a rate of 1000 stamps persecond. To eliminate stitching and other errors, the pattern is writtenfour times with offset grids and fields. Furthermore, the fields may beblended along the edges.

The mirrors are individually calibrated. A CCD camera, sensitive to theExcimer light, is placed in the optical path in a position equivalent tothe image under the final lens. The SLM mirrors are driven through asequence of known voltages and the response is measured by the camera. Acalibration function is determined for each mirror, to be used forreal-time correction of the grey-scale data during writing. In the datapath, the vector format pattern is rasterized into grey-scale images,with grey levels corresponding to dose levels on the individual pixelsin the four writing passes. This image can then be processed using imageprocessing. The final step is to convert the image to drive voltages forthe SLM. The image processing functions are done in real time usingprogrammable logic. Through various steps that have been disclosed inthe related patent applications, rasterizer pattern data is convertedinto values 103 that are used to drive the SLM 104.

FIG. 2 depicts a rotor scanning system with three arms and a pair ofworkpieces 211, 212 being written on opposite sides of the hub 248. Arotary printer as depicted may print 2D images on the workpiece. Thissystem may have a duty cycle of 100%. Each rotor writes through an arcof 60 degrees. Only one arm 240 writes at a time, alternatively on thetwo workpieces 211 and 212. The laser energy is switched by polarizationcontrol 232 between the two SLMs 247 and 249, and the data stream isalso switched between the SLMs. Since the laser 220 and the data path235 are among the most expensive modules in writing machines, thisembodiment has been designed to use laser and data channel 100% of thetime while the SLMs and the optics in the arms have lower duty cycles,50% and 33% respectively. This may be, for instance, an example of awriting system with three rotating arms 240A-C. There are a variety ofalternative designs for these arms and the relay optics. The figureconceptually depicts a laser 220 and a controller 235 sending data totwo SLMs 230 which are relayed 232, 247, 249 to the rotating arms. Itshows how each arm moves in front of each SLM and writes a series ofconcentric stamps on the workpieces 211, 212. While two workpieces areshown in this figure, more workpieces could be positioned under a rotor,depending on its size. While the example is described as a writingsystem, the direction of relay could just as easily be from theworkpiece back to a pair of detectors positioned where the laser 220 isand elsewhere. In alternative configurations, one workpiece might beused; four arms might be used.

Some particularly useful applications of this technology involve writingpatterns on electronic substrates, such as: wafers' front and backsides; PCBs; build-up, interposer and flexible interconnectionsubstrates; and masks, stencils, templates and other masters. Likewise,the rotor writer can be used for patterning panels in displays,electronic paper, plastic logic and photovoltaic cells. The patterningcan be done by exposure of photoresist, but also through other actionsof light such as thermal or photochemical processes: melting,evaporation, ablation, thermal fusing, laser-induced pattern transfer,annealing, pyrolytic and photo induced etching and deposition.

FIG. 3 depicts a generic data path. Data for a pixel-based exposuresystem that prints in a sequential manner is “flattened” (all datacontributing to one pixel aggregated) and localized. The patternrepresented as a rendered geometrical pixel map (GPM 121) fulfils theseproperties and makes a suitable format as intermediate storage.

A re-sampling process converts the GPM into modulator pixels in amodulator pixel map (MPM 123). Image processing and morphologicaloperations can also be applied during this re-sampling process. It ispossible to apply the image processing and morphological operations atboth local parts of the pattern, such as over the exposure system fieldof view, or globally over the pattern. The image processing andmorphological operations include, but are not limited to, scaling,translation, rotation, distortion and sizing. These operations can beused to compensate both for how the exposure system projects pixels ontothe mask/substrate and for properties of the mask/substrate.

Due to fidelity requirements and the potential information loss duringthe re-sampling process, the intermediate pixel map (GPM 121) has ahigher resolution than the Modulator Pixel Map (MPM 123). By usinggradient information in the re-sampling process, the memory resolutionrequired to satisfy the requirement of the GPM 121 can be significantlyreduced.

The majority of the pattern dependent processing steps are done duringgeneration of the GPM 121. The re-sampling is primarily used to handlelocalized pattern dependent (morphological) operations. It isadvantageous to limit re-sampling to localized pattern dependentoperations, as this improves the predictability of computational effortfor the re-sampling. Predictable computational effort, in turn, makes iteasier to optimize the configuration.

The use of the GPM 121 as intermediate storage enables exposure systemindependence, since processing steps to generate the GPM 121 can be madegeneric and independent from an exposure system.

Processing requirements for data paths in high resolutionmicrolithography are very challenging, even using the latest and mostcapable processing hardware. A contributing factor to success in highresolution processing and in high performance computing (HPC),generally, is parallelization. Parallelizing high resolution processinginvolves dividing the processing into small pieces. Microlithographyapplications that use the data paths described, process data that has ageographical property, which works within a coordinate system. Oneconvenient way to divide the task is coordinate oriented.

Processing according to the architecture disclosed can be described intwo domains, called off-line and on-line. Processing also operates indifferent data domains. In this disclosure, we refer to processing tocreate the geometrical pixel maps 121 as “GPM processing.” We refer toresampling of the GPM to create the modulator pixel map 123 as “MPMprocessing.” In the first phase of processing, operations are done in ageometrical coordinate system that is independent of modulator type andgeometry. The second phase is adapted to a particular modulator. Itproduces tiles that are pieces of modulator data arranged according torequirements from modulator.

When discussing the data path, we call the abutting parts of an area,covered by the pattern, “tiles” 510. Tiles can be fully described bygeometrical coordinates. We refer to tiles in both the GPM processingand the MPM processing, even though the coordinate systems could bequite different between the two.

In addition to the GPM 121 processing domain and MPM 123 processingdomain, a third data domain warrants discussion. The vector data domainprecedes rasterization to create the GPM. Therefore, the three differentdata domains are vector data, pixel data in a consolidated GeometricalPixel Map (the GPM) 121 and pixel data organized for the modulator (theMPM 123, Modulator Pixel Map).

Some Particular Embodiments

The technology disclosed includes a method of forming a custom latentimage in a radiation sensitive layer over a substrate. This methodincludes receiving standard data on a first data path and receivingcustom pattern data on a second data path. We intend for data paths tobe broadly construed. Standard pattern data is pattern data that isrepeatedly used for multiple dies or areas within a die and for multiplesubstrates in a batch, subject to customization. Custom pattern data isused to modify the standard pattern data to produce a custom latentimage. The method further includes resampling and merging the standardcustom pattern data to form a merged-rasterized pattern data thatrepresents the physical, custom latent image to be formed in a radiationsensitive layer. A latent image may be positive or negative, dependingon the resist or other radiation sensitive material applied over thesubstrate. In typical device manufacturing processes, a latent image isdeveloped and parts of the radiation sensitive layer removed to form apattern. The pattern is used to add or remove material as part offorming electronic devices.

The method further may include forming the custom latent image in theradiation sensitive layer from the merged-rasterized pattern data usinga direct writing device. Several samples of direct writing devices aregiven above and depicted in FIGS. 1-2. In addition, FIG. 5 depicts awide range of modulator types and scanning stages that could be combinedto produce direct writing devices not yet in production. We intend fordirect writing device to be broadly construed. The difference between adirect writing device and a more conventional stepper is that thestepper uses a mask or reticle, while the direct writing device uses amodulator as a virtual mask.

The standard and custom pattern data may be on aligned or offset grids.The pattern data of these types may use that the same or different pixelsizes. The simplest case is when the grids are aligned and coincident.Then, a pixel-to-pixel merge can be applied prior to resampling thedata. In some instances, it is necessary first to resample the standardand custom pattern data to aligned grids, to facilitate the merge. Theorder of merging and resampling, thus, depends on the particular databeing used to form a custom latent image.

The standard and custom pattern data can be processed in parallel,through separate pipelines. Or, they can be interleaved for dataretrieval and/or resampling, then merged.

Optionally, the resampling and merging can be performed in real-time. Byreal-time, we mean that the merging and/or resampling of the secondportion of data for a particular custom latent image happens as a firstportion of merged-rasterized pattern data, which is already beensubjected to merging and resampling, is being used to form a firstportion of the particular custom latent image. In real time, some of theresampling and merging for writing to a substrate is going on whilemerged-rasterized pattern data is being used to form part of the latentimage on the substrate.

As described above, the substrate can take a variety of forms. It can bea silicon or semiconductor wafer, circuit board, flat-panel display, ora flexible substrate used in so-called rule-to-roll production.

The method described can be applied one or more times to pattern one ormore layers over the substrate. After latent images are formed,conventional patterning processes are applied to form electronic deviceson the substrate. The method may be extended by using these processes toform electronic devices.

The custom data may be unique at a variety of levels. It may be uniqueto a particular die on a particular substrate, such as a serial number.It may be unique to a particular substrate, such as the time that theprinting of the layer begins. Or, it may be unique to a particular batchof substrates, such as a batch control number. Alternatively, customdata may be used with a large regular device, such as a memory chip or aflat-panel display, to finish edges of the pattern or to stitch togetheradjoining panels.

The technology disclosed also can be practiced as a controller adaptedto be linked to data paths and a direct writer. This controllerprocesses standard and custom pattern data according to any of themethods described above. The controller would include memory and aprocessor, whether a conventional CPU, RISC processor, FPGA, GPU, orother processing logic. Computer instructions are processed to merge andresample the standard and custom pattern data and output it for use by adirect writing device. The controller may be extended by combinationwith a direct writing device to form a writing system that practices anyof the methods described above.

The technology disclosed also can be practiced as non-transitorystorage, such as rotating or nonrotating memory, loaded with computerinstructions. The computer instructions may either be instructionsadapted to carry out any of the methods described above or adapted to becombined with hardware to produce the controller or writing systemdescribed above.

We claim as follows:
 1. A method of forming a custom latent image in apatterning layer over a substrate, the method including: receivingstandard pattern data on first data path; receiving custom pattern dataon a second data path; merging the standard and custom pattern data toform a merged-rasterized pattern data that represents a physical, customlatent image to be formed in a patterning layer; and forming the customlatent image in the patterning layer from the merged-rasterized patterndata using a direct writing device.
 2. The method of claim 1, furtherincluding applying the merging to a second portion of pattern data for aparticular custom latent image while a first portion ofmerged-rasterized pattern data is being used by the direct writingdevice to form a first portion of the particular custom latent image. 3.The method of claim 2, wherein the substrate is any of a silicon wafer,a semiconductor wafer, a circuit board, or a flat-panel display.
 4. Themethod of claim 2, wherein the substrate is a flexible material used inroll-to-roll production.
 5. The method of claim 1, wherein the standardpattern data represents a pattern field that repeats at a plurality ofadjoining locations sand the custom data represents a pattern edge. 6.The method of claim 1, wherein the standard pattern data represents apattern field that repeats at a plurality of adjoining locations and thecustom data represents a stitching area between the adjoining locations.7. The method of claim 1, wherein the substrate is any of a siliconwafer, a semiconductor wafer, a circuit board, or a flat-panel display,further including developing the custom latent image and forming one ormore electronic devices from the substrate.
 8. The method of claim 1,further including applying the receiving and forming actions one or moretimes, patterning layers over the substrate using the custom latentimages, and forming electronic devices using the patterned layers. 9.The method of claim 1, wherein the custom data is unique to a particularbatch of substrates.
 10. The method of claim 9, wherein the custom datais unique to a particular substrate.
 11. The method of claim 10, whereinthe custom data is unique to a particular die on a particular substrate.